Aims: Present study was to determine the effects of dietary energy source diets such as glucogenic and lipogenic nutrients on ruminal fermentation characteristics, venous blood gases and concentration plasma metabolites in Baluchi sheep. Study Design: Latin square design with 3 periods (28 days). Place and Duration of Study: Department of animal science, Faculty of agriculture, Ferdowsi University of Mashhad, between March 2012 and May 2012. Methodology: Experimental diets were a glucogenic, a lipogenic or a mixture of glucogenic and lipogenic diets (50:50). The animals were fed diets consisted of 50% chopped alfalfa hay and 50% concentrate. Ruminal fluid samples were collected before the feeding until 8 hour post feeding at day 24 of the each experimental period. Blood samples were taken from jugular vein before the feeding, 2, 4 and 6 h post feeding at day 26 of each period. In order to determine venous blood gases and pH, jugular blood samples were collected using heparinized syringes before and 4 h after feeding on day 27. Results: Results indicated that glucose and insulin concentration was decreased in sheep consume lipogenic diet (P<0.05). There were not significant differences between diets in regard of both ruminal pH and ammonia nitrogen concentration. Furthermore, blood pH and venous blood gases did not differ among diets (P>0.05). Conclusion: Feeding the mixture of glucogenic and lipogenic diets (50:50) improved

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